3' Nucleotide Asymmetry Directs miRNA Strand Selection

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• MicroRNA (miRNA) biogenesis involves processing double-stranded precursors into distinct guide and passenger strands.
• The guide strand directs the miRNA-induced silencing complex (miRISC) to mRNA targets, determining its function.
• Previous models based on 5' nucleotide identity and thermodynamics incompletely explain in vivo miRNA strand selection.

Purpose of the Study:

• To investigate the role of terminal nucleotide asymmetry in miRNA strand selection.
• To identify conserved mechanisms governing guide strand selection in vivo.
• To refine understanding of factors influencing miRNA targeting specificity.

Main Methods:

• Utilized Caenorhabditis elegans and human HEK293T cell models.
• Analyzed miRNA duplex processing and strand selection.
• Investigated the impact of 3' nucleotide variations on strand bias.

Main Results:

• Demonstrated a conserved role for 3' nucleotide asymmetry in miRNA strand selection across species.
• Showed that favorable 3' nucleotides on passenger strands promote guide strand selection.
• Identified terminal nucleotide asymmetries as key determinants of in vivo strand choice.

Conclusions:

• 3' nucleotide asymmetry is a significant conserved factor in miRNA strand selection.
• This mechanism contributes to accurate selection of the functional miRNA guide strand.
• Terminal nucleotide asymmetries on both miRNA strands collectively ensure precise target recognition by miRISC.